Production of smoke signs in the air



April 13, 1954 R. K. HANSEN ET AL 2,674,820

PRODUCTION OF SMOKE SIGNS IN THE AIR Filed Dec. 25, 1949 4 Sheets-Sheet 2 v AUDIO ELECTRONIC TRANSMITTER RECEIVER CONTROL OSCILLATOR ON-OFF sm. UNIT 6A c ON'TROL SELECTOR F|G 3 svs'rzu on uurr SELECTOR SMOKE suoxe SYSTEM CONTROL 7A coNTROL on UNIT A0010 5/6 MAL Am ur I a 6/20. I

T'-G'5 INVENTOR. I

C 0/1/71204 (/N/r M M M ATTORNEY U DIQQQE"- L"OL E 1 April 3, 1954 R. K. HANSEN ET AL 2,674,820

PRODUCTION OF SMOKE SIGNS IN THE AIR Filed Dec. 25, 1949 4 Sheets-Sheet 5 IN V EN TOR.

M BY 53% (Kr/K ATTORNEY April 13, 1954 R. K. HANSEN ET AL 2,674,820

PRODUCTION OF SMOKE SIGNS IN THE AIR Filed Dec. 23, 1949 4 Sheets-Sheet 4 208 l /NDICATOR 20A A/G a 2 I Q 44 I I I I I I I I I l I I I I I I FTMZZVIZVE' I 37 5 A I 49 7; l I

EST SWITCH o k t- I 6 SELECTOR SyS-rEM ATTORNEY Patented Apr. 13, 1954 PRODUCTION OF SMOKE SIGNS IN THE AIR Rolf Krohn Hansen, Bloomingdale, N. J., and Sale Sidney Pike, New York, N. Y.

Application December 23, 1949, Serial N 0. 134,816

3 Claims. 1

This invention relates to a method and apparatus for sky writers, particularly to that type of sky writing where a number of planes flying in formation cooperate in producing the letters. 7 According to the present invention a number of planes fly in parallel and with substantially equal speed following a straight line so that they are, at all times, aligned at right angles to the direction of flight. Each plane is equipped with smoke emitting apparatus. Emission of smoke is controlled to occur at short, regularly spaced time intervals. Means are provided to select these intervals for each plane prior to its flight so that the desired letters will be formed by the cooperation of the several smoke outlets. Each plane is provided with such a selector system, and one plane is further provided with a control for the synchronization of the performance of the several smoke outlets in the plurality of planes. Alternatively, this synchronizing or control signal may be provided by a station on the ground.

It is known to use a plurality of planes for forming the letters, each plane being assigned a certain part of each letter. art methods, records, similar to those used in player pianos, consisting of a blank provided with slots shaped in the pattern it is desired for the particular plane to write, are disclosed. This slotted blank is used to make and break an electric connection, thereby generating signals of a desired duration and placement. These signals are generated in a particular plane and are then transmitted to the other planes over separate channels, each signal .being transmitted to the plane for which it is intended. Thus, a number .of channels, one for each controlled plane, must be provided.

According to the present invention, it is not necessary to provide a plurality of channels, equal to the number of controlled planes, identical signals being sent to all participating planes. The signals transmitted according to the present invention serve to synchronize the various patterns for the different planes, the patterns to be determined by a selector system in each plane. Since an identical synchronizing signal is transmitted to all planes, the systeinaccording to this invention requires only one transmitting chan nel, independently of the number of participating planes. Hence, if in the prior system the diiferent patterns are transmitted over adjacent radio channels, a wide transmission band will be Fnecessary, whereas the present method will need .only a small fraction of this band which is made In these prior applicable to the entire number of participating planes. It will thus be appreciated that the separation of the two functions, the synchronization and the selection of the patterns, constitutes a considerable advantage over the prior art.

It is a further advantage of the present method that the selection is accomplished by standard commercially available parts, such as, for instance, a multi-contact switch, Whereas the prior systems required specially produced records. Changing from one message to another hence required the pattern record to be replaced so that separate records must be made for each message. The multi-contact switch, or other selector mechanism, used in the system according to this invention, will accommodate any message or other shapes it is desired to form.

Other advantages of the present method will become apparent in conjunction with the following specification and drawings.

Fig. 1 is a schematic View illustrating the formation of letters according to the present invention.

Fig. 2 is a front view of the panels carried by a plurality of planes.

Fig. 3 is a block diagram of the apparatus contained in the control plane and in the controlled planes, respectively.

Fig. 4 is a schematic diagram of part of the electronic apparatus in the control plane.

Fig. 5 is a schematic diagram of part of the electronic apparatus in each of the controlled planes.

Fig. 6 is a schematic diagram of the selector system and smoke control units.

Fig. 7 is a view of a plug-board showing the connections to stepping switches.

One manner in which the script is formed is illustrated in Fig. 1. Each letter is composed of suitably arranged short parallel lines of equal length, and the thickness of the heavy strokes in the letters may be approximately equal to the length of these short lines or a multiple thereof. The numbers to 150 in the first row of this figure indicate time intervals during which smoke may or may not be released. The numbers 1 to 7 in the first vertical row indicate the lane from which the smoke is emitted. It will be seen that any pattern composed of blank and smoke spaces may thus be ascribed to all planes, the patterns for two different planes being, in general different.

In the particular embodiment shown, the word Buyf. is outlined. The first plane will have to is indicated on the drawing. It will be seen that the selector panels are set up to make a connection for all those time intervals for which smoke is to be emitted from the associated plane, such as plugs 1, 2, 3, 4, 9, 10, 11 and 17 of the panel in plane 1; all other plugs are disconnected.

Fig. 3 shows a block diagram of the equipment, illustrating on the left-hand side the apparatus in the control plane, and on the right-hand side the apparatus in each of the controlled planes.

Alternatively the audio oscillator 2, electronic switch 3 and transmitter 4 may be installed on the ground, and all planes made to be controlled planes.

In the embodiment shown in Fig. 3, an audio frequency oscillation is generated by the audio oscillator 2 in the control plane. This oscillation is regularly interrupted by an electronic onoff switch 3 for approximately 0.6 second every 0.6 second. This time interval results in the desired length for the lines 1 if the planes fiy about 150 miles per hour. However, a different timing sequence may be preferred. The audio frequency pulses will be fed to the transmitter 4 which comprises a carrier generator, a modulator. w

and a transmitting antenna, all of conventional design and not shown.

The control unit 5 derives its input from the on-off switch 3 and advances the step selector system 6 by one step each 1.2 seconds, in the embodiment described, by means of a relay and solenoid arrangement more fully described and explained in connection with Fig. 4.

Referring again to Fig. 3, the step selector system 8 having been advanced, it will either make or not make a connection depending on the setting of the associated plug on the corresponding panel of the control or controlled plane, illustrated in Fig. 2. If a connection is made, a smoke control I will be operated and smoke will iii) escape; it no connection is made, no smoke will be emitted.

A similar control unit 5A, selector system 6A and smoke control IA are incorporated in each of the other planes, where they are controlled by a signal transmitted from the control and demodulated in the receiver 8.

Figs. 4, 5 and 6' illustrate detailsof a particular embodiment of this invention. Fig; 4, the control plane audio oscillator, electronic on-ofi switch, and switch control unit, shows the oscillator, comprising tubes H and I2, generating the audio oscillation. The output of this oscillator is fed to an amplifier tube l3. The grid bias of tube I3 is provided by a multivibrator I4, the output of which is rectified in tube l5 to give pulses, and interrupts the plate current of tube l3 for regular intervals of 0.6 second spaced 0.6 second.

This regularly interrupted audio frequency wave is fed to a conventional transmitter, comprising a carrier generator, a modulator, if necessary an amplifier for the modulated carrier, and an antenna; the transmitter is not shown.

The rectified multivibrator output also oper- 4 ates relays I5 and I! in the plate leads of tubes [8 and I9, respectively. Both tubes are normally cut-ofi, and both relays are normally open. Relay l6, when closed by a positive pulse on the grid of tube [8, applies 12 volts to the terminals A and F on plug 26 connecting to the selector system and smoke control unit shown in Fig. 6.

Relay l1-, when closed, connects 12 volts to the lamp 2|, flashing on every 0.6 second for 0.6 second, indicating that the multivibrator and rectifier operate satisfactorily.

Voice-tone switch 22 is operated by the pilot to open the relay 23 if the pilot of the control plane wants to communicate with the other pilots. Opening of this relay will interrupt current through tubes l8 and I3, cutting off all smoke supplies.

The circuit elements and their mode of operation of the audio oscillator and electronic on-ofl switch shown in Fig. 4 will now be described in more detail. Tubes II and I! with the associated circuit elements shown in Fig. 4 are connected together in such a manner as to form a conventional sine wave oscillator. The output voltage developed across plate load R3 is coupled through C-5 to a voltage divider potentiometer R-I 1. Such portion of this voltage as is desired is impressed on the grid of tube 13 and amplified. This amplified voltage is then fed to the input 01 the radio transmitter connector 50. Tube I3 is used to key the modulation signal. The keying is accomplished by periodically biasing the grid of l3 to cutoff.

The grid 01 tube 43 is connected to ground through resistors R-IZ and R44; the cathode is connected to ground through R43 and the contacts of relay 23. C-3 is a bypass for R-l3. Positive voltage from terminal B is applied to the plate of tube l3 through R-HI. With the contacts of relay 2-3' closed, plate current will dew and tube 13 will amplify the voltage applied to the grid through capacitor C-G. This amplified voltage isapplied through contact plug 50 to the input of radio transmitter 4 and modulates same.

The grid of tube I3 is also connected to the plates of diode l5. Tube M which is a conventional flip-flop circuit or square wave oscillator is coupled to the cathode of diode l5 through C-l2. Whenever the negative half of the square wave appears at the cathode of IS the diode conducts and applies a negative voltage to R-M. Sincethe grid of tube I3 is connected toground through Ply-2t a negative voltage on R-24 of sufficient amplitude will cut oil tube l3. By selecting the values of Rr-l l, R-IB, C-IB and CH tube II can be made to produce a square waveof a frequency suitable for turning on and off the modulation of transmitter 4.

The plate or tube It is connected to positive voltage terminal B through relay H5. The grid is connected to ground through l t-24 and 124-25 and the cathode is connected to ground through the contacts of relay 23. When the relay l3 is closed by switch 22 plate current will flow in tube l8 and operate relay It. When relay t3 closes, selector system 6 in Fig. 3 operates. When tube It is cut of! by a negative voltage on the grid, relay I6 opens and selector 6 is cut off and advances to the next step by spring action.

The plate of tube I3 is connected" to positive voltage terminal B- through relay II; the grid is connected to ground through R44 and 3-26. The cathode is grounded through R-fl. Plate current will flow in tube t3 and operate relay H. The contacts of relay l I v operate an indicator light on the pilots control board, indicating when the transmitter is being modulated. When the negative voltage from tube 4 cuts oil? tubes I3 and I8, tube I9 is also cut off, switching off indicator light 2|. R-22 and R-30 are decoupling resistors and C-I3 and C-l5 filter capacitors. R-28, lit-29 and C-|4, C-|4A are connected across the contacts of relay Hi to prevent arcing.

- Fig. 5 illustrates details of a control unit carried by the controlled planes. The received modulated carrier is applied to a conventional demodulator, not shown, and hence fed to terminal A of plug 24; terminal B of this plug is grounded.

The demodulated signal, which is a pulsed audio frequency, similar to the transmitted audio pulses, is amplified in tube 25, rectified in tube |5a, corresponding in its function to tube l5 in the equivalent section of the control plane con-. trol unit, and the resulting pulses, having been amplified in tube l8a, operate the relay I6a. Positive pulses, providing current through the relay solenoid, will close this normally open relay, connecting the 12 volts supplied to terminal B on plug 25a to terminals A and F on plug 26a. Terminal D on plug 25a and terminal E on plug 26a are grounded. Terminal B on plug 26a is permanently connected to terminal B on plug 25a, hence there are always 12 volts applied to this terminal. Plugs 25 and 26 in the control plane unit are similarly wired.

Fig. 5 shows the circuit diagram of control unit 5A used in the receiving planes. The control unit of Fig. 5 will now be described in more detail. The plate of tube 25 is connected to positive voltage terminal B through R-33. Screen voltage is obtained through R-34. The grid is connected to ground through potentiometer lit-3| and the cathode is grounded through R-32. Capacitors C-|6 and C-l3 are bypass capacitors for the screen and cathode resistors respectively. O IS couples the output of tube 25 to the plate of diode |5a and R-35 is the diode load. When a positive voltage is applied to the plate of diode [5a current will fiow to the cathode and through R-31 and R-36 to ground. The grid of tube |3a is connected through a bias battery 52 through R-36 to ground. The cathode of I8 is connected to ground and the plate connected to positive terminal B through relay coil |6A. The contacts of relay |6A controls plus 12 volts for the selector system 6A. Bias battery 52 normally cuts off tube |3a thereby leaving relay |6a open. When a positive voltage is applied to the plate of |5a of suflicient amplitude to overcome the bias voltage of 52, tube |8a will draw plate current and relay Ilia will close thereby operating the selector system. Plug 24 is connected to the audio output of receiver 8 and when an audio voltage is obtained from the receiver this is coupled through C-l1 to the grid of tube 25 amplified and rectified in tube l5a. Potentiometer lit-3| is used for adjusting to the proper value. When this signal is of suflicient amplitude it operates tube |8a which closes relay 6a which in turn controls the selector system. Capacitor R-20 is connected across R-36 to give a time constant for this circuit and prevent spurious noise voltages from operating tube l8a. Resistors R-38, R-39 and capacitors C-2I, C-22 are connected across the contacts of relay |6a to minimize arcing.

Fig. 6 shows the selector system and thesmoke control, which are identical for control and controlled planes.

The terminals of plug 263 are connected to the corresponding terminals or either plug 26 or plug 26A, dependin on whether it is on the control plane or on one of the other planes. Each positive 12 volt pulse on terminal A serves to advance the selector switch 21 by one step by means of solenoid 20, pushing sprocket wheel 28 ahead, and thereby rotating contact arms 29A, 29B, 29C, and 29E of stepping switch 21. There are 50 contacts on each-of the contact arms 29A to 29E of the particular switch illustrated, arms 29A, 29B and 290 being connected in series to provide contacts corresponding to the time intervals 1 to 150 indicated in Fig. 1; These figures are given as examples only and can be varied within wide limits.

Contacts 50, cooperating with each of the first four contact arms, are connected to the selector relay advance coil 30, pushing the armature 30A against the tension exerted by spring 30B, thereby advancing the ratchet wheel 4| by one step so that the lead 32 will be connected to the subsequent contact arm on switch 21.

The 12 volt pulses supplied by terminal F on plug 26B are fed by lead 32 to the contact arm 33A of switch 3|. This contact arm applies the pulses to either of contact arms 29A, 29B or 29C, in sequence, depending on its position. As illustrated in the embodiment shown in Fig. 6, the sky writer will have available for writing all contacts on the first three contact arms of switch 21, or 150' contacts, so that a'maximum of 150 lines can be produced by each plane.

It will be seen that the 12 volt pulses supplied to the contact arm's 29A to 290 are further supplied to the sockets in panel 34, a front view of which is shown in Fig. 2. The plugs 49 in these sockets having been set in each plane accordingto a predetermined line pattern, only those pulses where connections are provided will pass through leads 49 to lead 35 to operate the smoke valve relay 36 which will open the oil valve 31 for the duration of the pulse.

At the end of each period of writing, the two switches 21 and 3| must be reset to their initial positions. A manually operated reset switch 38 is provided for this purpose, its two contacts providing 12 volts DC. to the selector reset coil 39 and to the contact arm 29E of switch 21-, respectively.

Selector reset coil 39, operating against spring 40, causes the ratchet 4| to be released so that reset spring 42 will rotate switch 3| until spring 42 reaches its contracted position, when contact arms 33A and 33B bridge contacts If contact arm 29E is in position 1 while the D. C. voltage is applied, nothing will happen. In any other position of contact 29E, however, the D. C. voltage will be applied to the stepping switch advance coil 20, pushing its armature 20A to advance the ratchet wheel 28 by one step. Current through the relay 20 will further cause normally closed switch 43 to open. Opening of the switch 43 will in turn deenergize the relay coil 20, permitting spring 20B to retract the armature 20A and the switch 43 to close again, reestablishing current through the coil 20. This process is repeated until contact arm 2912. is in position 1, and the switch 21 is reset to its starting position. Completion of the resetting operation will be indicated by lamp 44 which will light only if both switches 21 and 3| are in their initial positions.

A test switch 45 for the smoke control valve 31 and associated elements is provided so that the pilot can ascertain whether or not the smoke valve and supply channels are in good order.

Depression of test switch 45 will apply 12 voltsv D; C. to the upper terminal of the valve relay 36 causin the valve to open. and smoke tobe released;

It will bev understood that the switching arrangement and the electronic circuitry shown and described as constituting a particular embodiment of this. invention should not be construed as limiting. It is desired that the invention be interpreted as broadly as the scope of the appended claims.

Having. thus described our invention, what we claim. and. desire to secure by Letters Patent is: as follows:

1. Apparatus for controlling the flow of a visiblei trace forming substance emitted by planes flying: in formation, comprising a control plane, an. audio oscillator in th control plane generating'audio frequency oscillations, a pulse generator in. the control plane supplying a succession of equal-length pulses, a modulator in the control plane fed by said oscillator andcontrolled by said pulse generator to generate a pulse-modulated audio'irequency oscillation, a transmitter in said control plane fed by said modulator, a plurality of controlled planes, a receiver in each of said controlled planes, a demodulator in said controlled, planes connecting to the receivers and restoring the succession of pulses, a direct current supply in each plane, a relay in each plane operatedby said succession of pulses, a stepping switch in each plane having one common terminal and a plurality of contacts successively connected to the common terminal when the switch is operated, a supply switch inserted between said directcurrent supply and said common terminal of the stepping switch in each plane, said supply switch being actuated-by said relay in each plane, an actuating mechanism in each plane for the stepping switch, said actuating mechanism being controlled by said relay and adapted, to advance the stepping switch by one step each time the relay is operated by one pulse in the succession of pulses, a plugboard with separable connectors leading to each of the plurality of contacts on the stepping switch selectively connecting each contact to a common terminal, and a smoke control mechanism connected to the common terminal.

2.. Apparatus" for controlling, the flow! at a viaible trace forming substance emitted by planes flying information as claimed; in claim 1, further comprising a reset mechanism for said stepping switch.

3. An apparatus for writing in the sky comprising a plurality of, planes in formation, means for emitting discreet smoke bursts, acontrolplane hav ng an oscillator for generating sinewave oscillations, an electronic switch for interrupting said oscillations at equal, and regularly spaced time intervals, a transmitter for transmitting said interrupted oscillations, a plurality of controlled planes, each having a receiver for receiving interrupted oscillations, a demolulator in said receivers for transferring said oscillations into audio pulses, a direct current supply in each plane, a relay in each plane operated by saidsuc' cession of, pulses, a stepping switch in each plane: having one common terminal and a plurality of contacts successively connected: to the common terminal when the switch is operated, a supply switch inserted between said direct current supply and said. common terminal of the stepping switch in each plane, said supply switch being; actuated by said relay in each plane, an actuating mechanism in each plane for the steppingswitch, said actuating mechanism being controlled by said relay and adapted to advance. the stepping switch by one step each time the relay is operated by one pulse in the succession of pulses, se-- lective switch means for producing a predetermined smoke pattern and smoke control means connected to said selective switch means for eiiecting said smoke pattern.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,346,493 Hammond July 1-3, 920 1,632,106 Zogbaum- June 14', 1927 1,769,060 Hendry July 1, 1930 2,063,354 'I'horp Dec. 8; 1936 2,184,387 Kiner Dec. 26; 1939 2,308,060 Rochefort Jan. 12, 1943 2,345,153 Remey Mar. 28, I944 

